Window coverings come in a variety of different styles and with various different functional features to best accommodate the functional need to control light and visibility through windows, as well as to provide convenience in adjustability of the window covering. Some window coverings are referred to as blinds and generally include slats therein which can be rotated in some such blinds to adjust an amount of light and visibility through the window covering. Other window coverings are generally in the form of shades which include a fabric or other planar material which can either occlude all light passing therethrough or be at least partially transparent. Shades can be planar in form or can have other geometric configurations. One such shade is formed of pleated fabric with the pleats running generally horizontally, allowing the shade to be retracted, accordion style, to allow for full visibility through the window, or deployed to completely or substantially completely cover the window.
With both shade type window coverings and blind type window coverings, control of retraction and deployment of the window covering is desirable. Often such window covering position adjustability is facilitated by suspending a bottom rail or other bottom member of the window covering from at least one cord, and typically multiple cords, extending vertically up from the bottom rail to a top rail or other upper portion of the window covering which is secured to the lintel. Because the bottom member is suspended by this cord (or cords), tension can be applied to the cord and the cord shortened to lift the bottom member and cause the window covering to the retracted. Conversely, slackening the cord allows the bottom rail to move down and for the window covering to be more fully deployed. While the bottom rail is usually fixed to an end of the cord, it can alternatively be attached to the cord in a movable fashion where the cord remains generally stationary and the bottom rail moves up and down on the cord to retract or deploy the window covering.
Various different styles of bottom rail cord suspension mechanisms are known in the prior art. Some of these systems include locking and unlocking members in the top rail so that when the cord is locked the bottom rail remains in fixed position and when the cord is unlocked it, it can be pulled or released to raise or lower the bottom rail. Standard prior art “Venetian blinds” often exhibit variations on such a cord suspension and lifting mechanism. Because excessive cord can be unsightly and potentially dangerous, especially to young children, many shades include cords which are collected within one of the rails. Typically, such window coverings include buttons on the bottom rail which act to lock or unlock the cords and allow for positioning of the bottom rail. Representative of such window coverings are U.S. Pat. Nos. 6,823,925 and 7,331,370. While such internal cord collection within the rails can be achieved, it requires complex mechanisms which are subject to potential failure and significantly increase the cost of the window covering. Cords which lock at the top rail and which are pulled to raise the window covering, have the undesirable effect of the cord being rather long when the shade is retracted, bringing the cord lower and into potential dangerous contact with children or animals. Furthermore, when shades require that buttons be pushed, manipulation of the shade typically requires two hands for proper operation. Accordingly, a need exists for window coverings which are adjustable but which minimize exposed cord, the use of buttons, and preferably can be retracted or deployed merely by pushing or pulling on the bottom rail.
Furthermore, window coverings which include cord handling mechanisms within rails thereof typically require relatively large volume rigid extrusions or other complex rigid structures and relatively large complex assembly. Accordingly, a need exists for a window covering with rails that are of a simple form but can still contain cord handling mechanisms therein and which can be easily manufactured from low cost materials. Such window coverings would also benefit from being easily sized by a user to match window width.